As an apparatus for performing various processing operations on a substrate, such as a film-forming operation, an etching operation, and the like, there is conventionally known an apparatus (so-called cluster tool apparatus) in which: as shown in FIG. 1, a plurality of load lock chambers A, B and a plurality of processing chambers C through F are disposed so as to enclose a central transfer chamber T in which is disposed a transfer robot 1; and a substrate S charged or fed into the load lock chamber A, B is transferred to the processing chambers C through F or among the processing chambers C through F by the transfer robot 1.
In this kind of apparatus, it is known that the state for the transfer robot to wait for a substrate to finish processing operation (so-called processing rate controlling) and the state for the transfer robot to wait for the substrate to be transferred out of the processing chamber (so-called transfer rate controlling) have effects on the processing capacity (throughput) of the processing apparatus. If the arrangement of the processing apparatus becomes complicated, the above-mentioned processing rate controlling and the transfer rate controlling will occur at a plurality of places. When the substrate is continuously processed, the total sum of the transfer time and the processing time, when due attention is paid to each of the substrates, are said to be the maximum processing capacity of the processing apparatus.
In order to improve the processing capacity of the processing apparatus, like in the processing apparatus as shown in FIG. 1, it is known to use a transfer robot having two robot hands for supporting the substrates (see, e.g., patent document 1). By using two robot hands, the transfer rate controlling can be minimized.
In this kind of processing apparatus, the transfer robot performs a single action in accordance with a single command that is issued from a host computer. In other words, in case a substrate that is present in one processing chamber is transferred to another processing chamber, the transfer robot used to perform a plurality of actions in accordance with the commands such as “pick,” “go to,” “place” and the like. Whenever each of the actions of the transfer robot is finished, communication used to be made between the transfer robot and the host computer. Therefore, in the conventional method of controlling a transfer robot, the number of communication between the transfer robot and the host computer is large and the transfer time becomes longer by the time that is required for the communication. Therefore, there was a problem in that the throughput is lowered.